IP addresses

Network Layer 4-2

4.1 introduction4.2 virtual circuit and datagram networks4.3 what’s inside a router4.4 IP: Internet Protocol

• datagram format• IPv4 addressing• ICMP• IPv6

4.5 routing algorithms• link state• distance vector• hierarchical routing

4.6 routing in the Internet• RIP• OSPF• BGP

4.7 broadcast and multicast routing

Chapter 4: outline

Network Layer 4-3

IP addressing: introduction

• IP address: 32-bit identifier for host, router interface

• interface: connection between host/router and physical link

• routers typically have multiple interfaces

• host typically has one active interface (e.g., wired Ethernet, wireless 802.11)

• one IP address associated with each interface

223.1.1.1

223.1.1.2

223.1.1.3

223.1.1.4 223.1.2.9

223.1.2.2

223.1.2.1

223.1.3.2223.1.3.1

223.1.3.27

223.1.1.1 = 11011111 00000001 00000001 00000001

223 1 11

Network Layer 4-4

IP addressing: introduction

Q: how are interfaces actually connected?A: we’ll learn about that in chapter 5, 6.

223.1.1.1

223.1.1.2

223.1.1.3

223.1.1.4 223.1.2.9

223.1.2.2

223.1.2.1

223.1.3.2223.1.3.1

223.1.3.27

A: wired Ethernet interfaces connected by Ethernet switches

A: wireless WiFi interfaces connected by WiFi base station

For now: don’t need to worry about how one interface is connected to another (with no intervening router)

Network Layer 4-5

Subnets

• IP address: • subnet part - high order

bits• host part - low order

bits

• what’s a subnet ?• device interfaces with

same subnet part of IP address

• can physically reach each other without intervening router

network consisting of 3 subnets

223.1.1.1

223.1.1.3

223.1.1.4 223.1.2.9

223.1.3.2223.1.3.1

subnet

223.1.1.2

223.1.3.27223.1.2.2

223.1.2.1

Network Layer 4-6

recipeto determine the

subnets, detach each interface from its host or router, creating islands of isolated networks

each isolated network is called a subnet

subnet mask: /24

Subnets223.1.1.0/24

223.1.2.0/24

223.1.3.0/24

223.1.1.1

223.1.1.3

223.1.1.4 223.1.2.9

223.1.3.2223.1.3.1

subnet

223.1.1.2

223.1.3.27223.1.2.2

223.1.2.1

Network Layer 4-7

how many? 223.1.1.1

223.1.1.3

223.1.1.4

223.1.2.2223.1.2.1

223.1.2.6

223.1.3.2223.1.3.1

223.1.3.27

223.1.1.2

223.1.7.0

223.1.7.1223.1.8.0223.1.8.1

223.1.9.1

223.1.9.2

Subnets

Network Layer 4-8

IP addressing: CIDR

CIDR: Classless InterDomain Routing subnet portion of address of arbitrary length address format: a.b.c.d/x, where x is # bits in

subnet portion of address Practice: use the command line tool ipconfig

11001000 00010111 00010000 00000000

subnetpart

hostpart

200.23.16.0/23

Network Layer 4-9

IPv6: motivation• initial motivation: 32-bit address space soon to be

completely allocated. • 2^32 = 4.294.967.296• Internet of Things requires a lot of IP addresses• Addresses are allocated in (large) series, not one-by-one

• additional motivation:• header format helps speed processing/forwarding• header changes to facilitate QoS

IPv6 datagram format: • 128-bit address• 2^128 = 3.4*10^38